In order to improve pulping liquor penetration and avoid production of uncooked "knots", pulp chips are commonly screened and the overthick chips removed. The overthick chips may then be sliced to reduced thickness or they may be fed to compression rolls before they are returned into the digester fissures stream. Compression rolls partially crush the chips and open many surface cracks or fissures that allow more ready liquor penetration. The quality of sliced chips is easily monitored using conventional chip classification testing; e.g., as shown in Marrs U.S. Pat. No. 4,487,323. Compression rolls fissure the chips but do not significantly alter their size distribution. For this reason their quality is not easily monitored using conventional size classification methods. Up to the present time, compression roll effectiveness could only be monitored by pulping the chips and noting changes in pulp yield or other properties.
Screened yield is a direct function of how well chips absorb liquor. Where compression roll treated oversize chips are concerned, roll surface configuration and wear, nip settings, and effects of loading rates all affect chip absorbency characteristics. Thus, a fast and simple test method suitable for mill use that would readily and accurately indicate liquor absorbency properties would be of considerable value. The present invention is directed to that end.